Practice exam 1 Chem
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J.J Thomson is credited with discovering the electron: T/F
TRUE

Two isotopes of the same element can have a different number of protons:T/F
FALSE

Two isotopes of the same element can have a different number of electrons: T/F
TRUE

The symbol for magnesium is Mn : T/F
FALSE

As5+ has 33 protons and 28 electrons : T/F
TRUE

The answer to the following mathematical operation (18.511.4) has three significant figures: T/F
FALSE

A homogeneous mixture can be made by completely dissolving salt into water : T/F
TRUE

It is impossible to round 45,629.54 to three significant figures : T/F
FALSE

The density of a pure compound changes depending on how much liquid is present: T/F
FALSE

A mass of 456.2 g of brass (72% copper, 28% zinc) contains 328.5 g zinc: T/F
FALSE

An increase of 1°F corresponds to an increase of 1.8°C : T/F
FALSE

A hypothesis will predict the outcome of all future experiments : T/F
FALSE

Perform the following calculations and indicate the results to the correct number of significant figures:
1.24 x 3.796 =
4.70704 = 4.71

Perform the following calculations and indicate the results to the correct number of significant figures.
4.17 + 13.1 + 6.14 =
23.41 = 23.4

Perform the following calculations and indicate the results to the correct number of significant figures.
(14.35 – 7.12) x (12.3 + 3.58) =
7.23 x 15.88 = 114.8124 = 115

convert to standard:
1.403 x 103
1403

covert to standard:
2.85 x 104
0.000285

covert to standard:
1.67 x 102
0.0167

convert to scientific notation:
1.259 x 103
1259

convert to scientific notation:
4.6 x 103
0.0046

convert to scientific notation:
2.10006 x 101
21.0006

523 nm to m
 523nm x 10^{9}m = 5.23 x 10^{7} m
 1nm

219 K to°F
 °C = 219273 =54°C
 °F= (54 x 1.8) +32= 65.2°F

66 mi/hr to km/s
 66mi x 1.609km x 1hr x 1min = 0.029km/s
 hr 1.0mi 60min 1sec

1 year to seconds (Scientific Notation)
 1yr X 365.2days X 24hr X 60min X 60s=3x10^{7}s
 1yr 1day 1hr 1min

Magnesium has three naturally occurring isotopes 24Mg (78.99%), 25Mg (10.00%), and 26Mg (11.01%). What is the isotopic mass of 25Mg if the mass of 24Mg is 23.985 amu and the mass of 26Mg is 25.983 amu?
 23.985amu (0.7899) + x(0.100)
 + 25.938amu (0.1101) = 24.31amu
 x= 24.31amu  18.946  2.856= 25.08amu
 0.100